1. Field of the Invention
The present invention relates to a use of a stem cell conditioned medium to induce ZO-1 proteins expression for skin regeneration, repair and firming. The conditioned medium obtained from human Wharton's jelly-derived mesenchymal stem cells (WJMSCs) conditioned basal medium can effectively increase the activation of tight junction protein Zonula occludens-1 (ZO-1) in skin cells so as to improve users' undesired skin conditions, e.g. slack skin.
2. Description of Related Art
Due to the increase in life expectancy, how to slow down aging has become one of important issues in medicine. In mammals such as humans, skin is the soft outer covering all over a mammal body and enables to interface with the environment as the first line of defense from external factors. Therefore, skin is the most vulnerable organ to external stimuli and UV damage. Skin reflects the physiological state, mental state as well as the age of individuals. When skin is lack of water, it often leads to aging, rough, loose or wrinkle formation. The young and tight skin, which often presents a shining gloss, usually makes people look spirited. However, with increasing ages, skin may gradually reveal weakness, dullness, wrinkles or sagging owing to the loss of natural moisturizing factors, cells disarrangement, and poor water retention capacity in epithelia. Therefore, in addition to whitening, recently people also focus on the maintenance of skin firmness. In the dermis, there are two important proteins, collagen and elastin, which support skin and make it plump and firm. However, these two proteins will naturally decrease with age, and fibers among cells will be also degraded with time, resulting in the loss of elasticity and firmness of skin.
Nowadays, there are various methods for treating sagging and wrinkling of skin, including laser facelift, injections of Botox, hyaluronic acid or collagen, or supplements with growth factors. For instance, U.S. Pat. No. 4,959,353, issued on 25 Sep. 1990, disclosed a “Promotion of corneal stroma wound healing with human epidermal growth factor prepared from recombinant DNA.” It describes the use of epidermal growth factor for treatment of corneal wounds. U.S. Pat. No. 5,130,298, issued on 14 Jul. 1992, disclosed a “Stabilized compositions containing epidermal growth factor.” It shows that the compositions containing epidermal growth factors can be used stably against decomposition of the metallic cations for treating wounds. U.S. Pat. No. 5,104,977, issued on 14 Apr. 1992, disclosed a “Purified transforming growth factor beta.” It describes the use of the transformation growth factor β (TGF-beta) or transformed cells growth factor α (TGF-alpha) to the treatment of injured tissue. However, protein growth factors cannot be used to reduce the aging of the non-flaking or non-injured skin. In addition, most methods of treating sagging and wrinkling of the skin are expensive and must require experts to conduct treatment. Moreover, patients require a period of time for recovery after the treatment.
In these years, studies of stem cells have been a growing trend in the world. Stem cells can mainly be divided into two categories, embryonic stem cells and adult stem cells. Mesenchymal stem cells (MSCs) belong to adult stem cells and have a great potential for differentiation. MSCs can differentiate into not only tissues (such as skeleton) derived from mesoderm, but also visceral cells (such as liver and pancreas) derived from endoderm and neurons derived from ectoderm. MSCs are ubiquitous in adults' bodies and can be isolated from bone marrows and various organs. However, the number of MSCs in the bodies is small, and adults' MSCs are known to gradually decrease with the age of the donors. Therefore, how to obtain a sufficient amount of MSCs becomes very important. Bone marrow MSCs are mainly derived from adult bone marrow, but invasive ways to get the bone marrow MSCs may cause pain and discomfort to donors. Umbilical cords contain a number of rich and young MSCs with strong differentiation potential, so they can be used as an important source of mesenchymal stem cells. In comparison with obtaining MSCs from bone marrows, obtaining MSCs from umbilical cords is relatively easy. Moreover, recent studies showed that human mesenchymal stein cell-derived conditioned medium (MSC-CM) can enhance corneal endothelial cells proliferation. This conditioned medium can increase expression of tight junction proteins and effectively assist cells in their normal arrangement and growth.